Ethylene signaling plays an important role in UV-B-induced ascorbic acid accumulation in Cucumis Sativus leaves

UV-B regulates the metabolism of many important substances, such as hormones, ascorbic acid (AsA) and secondary metabolites. However, the mechanism by which UV-B regulates AsA metabolism, especially signal transduction, is largely unclear. Here, we report that UV-B promotes the accumulation of AsA and the production of ethylene in cucumber seedlings. However, when the ethylene signal is blocked, UV-B no longer promotes the accumulation of AsA in cucumber leaves. This indicates that the ethylene signal is a key factor enabling UV-B to regulate AsA levels. The q-PCR results show that UV-B induces the expression of the CsACO and CsACS genes, which, in turn, promotes the biosynthesis of ethylene; thus, ethylene production is promoted and the ethylene signal is activated. Moreover, the expression of the ethylene response factor CsERF39 is up-regulated through a series of UV-B signal transduction. Knockout of CsERF39 and CsGLDH results in a reduced AsA pool in cucumber leaves. Furthermore, we identified CsGLDH as a direct target for CsERF39 to regulate AsA biosynthesis, by q-PCR analysis, molecular experiments and genetic data. Therefore, CsACS , CsACO , CsERF39 and CsGLDH are involved in the regulation of AsA biosynthesis by UV-B through the ethylene signal transcription cascade.